1. Field of the Invention
The present invention relates to improvements in a laser beam scanning system and, more particularly, to a laser beam scanning system which is so improved that it can scan a large area at a high speed and with high accuracy using a finely focused laser beam.
2. Description of the Prior Art
Some of the laser beam scanning systems according to the prior art make use of a polygon mirror or resort to the reciprocating mechanical motions of an objective lens. In the former scanning system using the polygon mirror, a biaxial scanning operation is performed by effecting both one scanning operation over a large field in a wide angle range in one direction with a lens having a large F-.theta. value and another scanning operation at a right angle in a manner to drive a specimen to be scanned in a continuous mode or in a step-and-repeat mode with the use of a carriage. In this case, the scanning speed is high, but the diameter of the focused laser beam spot is so large as to raise problems relating to the scanning accuracy and the resolution. In the latter scanning system, on the other hand, the scanning operation over a large field is performed by effecting reciprocating mechanical motions of the objective lens in a plane in parallel with the specimen surface. In this case, since the system can use an objective lens having a high numerical aperture (N.A.), the laser probe diameter is so small as to provide an excellent resolution, but the there arises problems in the scanning speed and accuracy because of the mechanical motions.